Polymethacrylimide plastic foam materials with reduced inflammability in addition to a method for the production thereof

ABSTRACT

The present invention relates to compositions for producing poly(meth)acrylimide foams having reduced flammability which comprise ammonium polyphosphate and/or zinc sulphide. Furthermore, the present invention also provides poly(meth)acrylimide moulding compositions and also poly(meth)acrylimide foams obtainable from the abovementioned compositions and moulding compositions. The present invention further relates to processes for producing poly(meth)acrylimide foams having reduced flammability.

FIELD OF THE INVENTION

The invention relates to compositions for producing polymethacrylimidefoams having reduced flammability, to polymethacrylimide mouldingcompositions, polymethacrylimide foams and also to processes forproducing the abovementioned products.

PRIOR ART

Polymethacrylimide foams have been known for some time and, owing totheir outstanding mechanical properties and their light weight, find awide range of use, in particular in preparing layered materials,laminates, composites, or foam composites. Prepregs are frequentlycombined with polymethacrylimide core materials.

For example, prepregs are used in aircraft building, shipbuilding andalso in buildings. For many of these numerous applications, they have tosatisfy fire protection requirements laid down in statutory directivesand a series of other regulations.

To prove that the foams satisfy the fire protection requirements, avariety of different fire tests are carried out which are customarilydirected to the use of the foam or the composite containing it. Ingeneral, it is necessary to provide the polymethacrylimide foams withflame retardants so that these tests are passed.

The use of chlorine or bromine compounds as flame retardants is widelyknown. These compounds are frequently used together with antimonyoxides. However, a disadvantage is that polymethacrylimides whoseflammability is reduced in this way can only be very poorly recycled,since these halohydrocarbons can scarcely be removed from the polymerand, in waste incineration plants, dioxins can form from thesecompounds.

Furthermore, in the event of fire, poisonous gases, for example, HCl andHBr, are formed. Owing to these disadvantages, it is a general aim tovery substantially avoid chlorinated and brominated substances asadditives in plastics.

Phosphorus compounds are a further substance class of flame retardantswith which polymethacrylimide foams are provided. However, a particulardisadvantage is that fire results in a very high smoke density whichlikewise occurs in the case of halogenated flame retardants. Owing toits toxicity, this smoke on the one hand endangers people who breathe inthese gases and on the other hand hampers rescue work.

In addition, many of the phosphorus compounds used as flame retardantsfunction as plasticizers. This undesired effect limits the amount ofphosphorus compounds added.

Furthermore, the flame-retardant polymethacrylimide foams known hithertodo not fulfil all of the fire protection standards required for certainapplications. For example, although existing foams which are obtainedaccording to DE-A 33 46 060, EPA 0 146 892 or U.S. Pat. No. 4,576,971are self-extinguishing, they comply only unsatisfactorily, if at all,with the vertical flame test 60s according to FAR 25.853(a) (1) (i) orthe smoke density test according to FAR 25.853(c), AITM 2.0007 andexhibit high heat development according to FAR 25.853(c). In thisconnection, there is in particular a remarkably high dependency upon thedensity of the test sample. Although foams having high density sometimespass the vertical flame test 60s, they exhibit very high heatdevelopment. The abovementioned materials do not pass the fire test forrail vehicles according to DIN 54837.

The PMI foams described in the German patent application no. 10052239.4are also unsatisfactory in relation to their flame resistance. Theformulations having expandable graphite cited there lead to foams whichfirstly release too large an amount of heat during the combustion (theamount of heat released corresponds to twice the amount allowedaccording to FAR 25.853(c)) and secondly lack mechanical stability incomparison to PMI foams existing on the market. Further, the expandablegraphite used for flame retardancy cannot be introduced into thematerial homogeneously, since the use of a dispersant comminutes theexpandable graphite particles and thus distinctly reduces the flameretardancy. (It is generally known that the expanding action ofexpandable graphite reduces with falling particle size and the flameretardancy is thus worsened.) The nonhomogeneous foam slabs have to bemanually straightened, which however leads to very many rejects owing tomaterial fracture, i.e. ˜80% of the foam slabs produced cannot be usedfor application purposes.

Object

In view of the prior art cited and discussed herein, it is an object ofthe present invention to provide compositions for producingpolymethacrylimide foams having reduced flammability, polymethacrylimidemoulding compositions and also polymethacrylimide foams which exhibitlow smoke development according to FAR 25.853(c), AITM 2.0007 and alsolow heat development according to FAR 25.853(c). Furthermore, the foamsshall pass the vertical flame test 60s according to FAR 25.853(a)(1)(i).

Another problem is to provide polymethacrylimide foams which satisfy thestandards of the fire test for rail vehicles according to DIN 54837.

Another object of the invention is to provide polymethacrylimide foamshaving reduced flammability which comprise reduced amounts of phosphoruscompounds or halogenated hydrocarbons.

A further object of the invention is to provide a very inexpensive flameretardant for polymethacrylimides and/or polymethacrylimide foams.

Furthermore, it is therefore an object of the present invention that theflame retardant used to treat the polymethacrylimides orpolymethacrylimide foams shall be very substantially acceptable underhealth considerations. The mechanical properties of the foams accordingto the invention shall further not be adversely affected by theadditives.

Solution

The abovementioned object can be achieved by foams which are preparedaccording to the process described in the German patent application no.10113899.7. This quite generally discloses a means of introducinginsoluble additives into PMI foams produced by the cell process.However, the disclosed formulations provide no application utility.

When the additives used are ammonium polyphosphate or combinations ofammonium polyphosphate and zinc sulphide, the PMI foams obtained have adistinctly reduced heat emission according to FAR 25.853(c). The amountof ammonium polyphosphate alone which is used, based on the total amountof monomers, is between 0.1 and 350% by weight of ammoniumpolyphosphate, preferably between 5 and 200% by weight of ammoniumpolyphosphate and more preferably between 25 and 150% by weight ofammonium polyphosphate.

The amount of zinc sulphide alone which is used, based on the totalamount of monomers, is between 0.1-20% by weight of zinc sulphide,preferably between 0.5-10% by weight of zinc sulphide and morepreferably between 1-5% by weight of zinc sulphide.

When both substances are used as a mixture, the ammonium polyphosphatecontent is 1-300% by weight and the zinc sulphide content is 0.1-20% byweight, preferably 5-200% by weight of ammonium polyphosphate and0.5-10% by weight of zinc sulphide and more preferably 25-150% by weightof ammonium polyphosphate and 1-5% by weight of zinc sulphide.

Ammonium polyphosphates (NH₄PO₃)_(n) (n=20 to approx. 1000) are thecondensation products of the corresponding orthophosphates. The use ofthese water-insoluble compounds as flame retardants for paints,synthetic resins and wood is known (Römpp, 10th Edition, (1996),Ullmann, 4th Edition (1979)).

Further flame retardants may optionally be used individually or inmixtures. Examples of further flame retardants that may be used includephosphorus compounds, for example, phosphines, phosphine oxides,phosphonium compounds, phosphonates, phosphites or phosphates.

In addition to ammonium polyphosphate and zinc sulphide, the compositionaccording to the invention may comprise further flame retardants inorder to additionally reduce flammability. These flame retardants arewidely known to those skilled in the art. In addition to halogenatedflame retardants which sometimes comprise antimony oxides, phosphoruscompounds may also be used. Owing to the better recyclability of theplastics, preference is given to phosphorus compounds.

Phosphorus compounds include phosphines, phosphine oxides, phosphoniumcompounds, phosphonates, phosphites and/or phosphates. These compoundsmay be of organic and/or inorganic nature, and include derivatives ofthese compounds, for example, phosphoric monoesters, phosphonicmonoesters, phosphoric diesters, phosphonic diesters and phosphorictriesters and also polyphosphates.

Preference is given to phosphorus compounds of the formula (I)X—CH₂—P(O)(OR)₂  (I)where each R is an identical or different radical from the group ofmethyl, ethyl and chloromethyl, and X is a hydrogen or halogen atom, ahydroxyl group or an R¹O—CO— group where R¹ is methyl, ethyl orchloromethyl.

Examples of phosphorus compounds of the formula (I) include dimethylmethanephosphonate (DMMP), diethyl methanephosphonate, dimethylchloromethanephosphonate, diethyl chloromethanephosphonate, dimethylhydroxymethanephosphonate, diethyl hydroxymethanephosphonate, dimethylmethoxycarbonylmethanephosphonate and diethylethoxycarbonylmethanephosphonate.

The phosphorus compounds may be used individually or as a mixture.Preference is given in particular to mixtures which comprise phosphoruscompounds of the formula (I).

These compounds may be used up to a proportion of 25% by weight, basedon the weight of the monomers, in order to satisfy the fire protectionstandards. In preferred embodiments, the proportion of phosphoruscompounds is in the range from 1-15% by weight, although this is notintended to imply any restriction. The use of increasing amounts ofthese compounds may worsen the other thermal and mechanical propertiesof the plastics, for example the compressive strength, the flexuralstrength and heat distortion resistance.

Compositions according to the invention for producingpoly(meth)acrylimide foams are polymerizable mixtures which comprise atleast one, customarily two or more, monomers, for example (meth)acrylicacid and (meth)acrylonitrile, blowing agent, at least one polymerizationinitiator and ammonium polyphosphate and/or zinc sulphide, with orwithout further flame retardants. These compositions are polymerized toprecursors from which poly(meth)acrylimide foams are formed by heating.

The notation in brackets is intended to indicate an optional feature.For example, (meth)acrylic means acrylic, methacrylic and mixtures ofboth.

The poly(meth)acrylimide foams obtainable from the compositionsaccording to the invention have repeating units which can be representedby formula (II)

wherein

-   R¹ and R² are the same or different and are each hydrogen or a    methyl group, and R³ is hydrogen or an alkyl or aryl radical having    up to 20 carbon atoms.

Units of the structure (II) preferably form more than 30% by weight,more preferably more than 50% by weight and most preferably more than80% by weight, of the poly(meth)acrylimide foam.

The production of rigid poly(meth)acrylimide foams is known per se andis disclosed, for example, in GB Patent 1 078 425, GB Patent 1 045 229,DE Patent 1 817 156 (=U.S. Pat. No. 3,627,711) or DE Patent 27 26 259(=U.S. Pat. No. 4,139,685).

For instance, one way of forming the units of the structural formula(II) from neighbouring units of (meth)acrylic acid and(meth)acrylonitrile is by a cyclizing isomerization reaction on heatingto 150 to 250° C. (cf. DE-C 18 17 156, DE-C 27 26 259, EP-B 146 892).Customarily, a precursor is initially obtained by polymerizing themonomers in the presence of a radical initiator at low temperatures, forexample 30 to 60° C. with post-heating to 60 to 120° C. and theprecursor is then foamed by a blowing agent present on heating toapprox. 180 to 250° C. (see EP-B 356 714).

To this end, for example, a copolymer may initially be formed whichcomprises (meth)acrylic acid and (meth)acrylonitrile, preferably in amolar ratio between 1:4 and 4:1.

Furthermore, these copolymers may comprise further monomer units which,for example, arise from esters of acrylic or methacrylic acid, inparticular with lower alcohols having 1-4 carbon atoms, styrene, maleicacid or anhydride, itaconic acid or anhydride, vinylpyrrolidone, vinylchloride or vinylidene chloride. The proportion of comonomers which canonly be cyclized with great difficulty, if at all, should not exceed 30%by weight, preferably 20% by weight and more preferably 10% by weight,based on the weight of the monomers.

Further polymers which can likewise be used advantageously in a knownmanner include small amounts of crosslinkers, for example, allylacrylate, allyl methacrylate, ethylene glycol diacrylate ordimethacrylate or polyvalent metal salts of acrylic or methacrylic acid,such as magnesium methacrylate. The proportions of these crosslinkersare frequently in the range from 0.005 to 5% by weight, based on thetotal amount of polymerizable monomers.

Furthermore, metal salt additives may be used. These include theacrylates or methacrylates of alkaline earth metals or zinc. Preferenceis given to zinc (meth)acrylate and magnesium (meth)acrylate. Thepolymerization initiators used are those which are themselves customaryfor the polymerization of (meth)acrylates, for example azo compoundssuch as azodiisobutyronitrile, and also peroxides such as dibenzoylperoxide or dilauroyl peroxide, or else other peroxide compounds, forexample, t-butyl peroctanoate or perketals, or else optionally redoxinitiators (on this subject, cf., for example, H. Rauch-Puntigam, Th.Völker, Acryl- und Methacrylverbindungen, Springer, Heidelberg, 1967 orKirk-Othmer, Encyclopedia of Chemical Technology, Vol. 1, pages 286 ff,John Wiley & Sons, New York, 1978). Preference is given to using thepolymerization initiators in amounts of from 0.01 to 0.3% by weight,based on the total weight of the monomers used.

It may also be advantageous to combine polymerization initiators havingdiffering decomposition properties with regard to time and temperature.It is highly suitable, for example, to use at the same time tert-butylperpivalate, tert-butyl perbenzoate and tert-butyl per-2-ethylhexanoate,or tert-butyl perbenzoate, 2,2-azobisiso-2,4-dimethylvaleronitrile,2,2-azobisiso-butyronitrile and di-tert-butyl peroxide.

The polymerization is preferably effected via variants of bulkpolymerization, for example, the cell process, without being restrictedto them.

The weight average molecular weight {overscore (M)}_(w) of the polymersis preferably greater than 10⁶ g/mol, in particular greater than 3×10⁶g/mol, although no restriction is intended.

During the conversion to an imide-containing polymer, blowing agentswhich form a gas phase by decomposition or evaporation at 150 to 250° C.serve in a known manner to foam the copolymer. On decomposition, blowingagents having amide structure, such as urea, monomethyl- orN,N′-dimethylurea, formamide or monomethylformamide release ammonia oramines which can contribute to additional formation of imide groups.However, it is also possible to use nitrogen-free blowing agents such asformic acid, water or monohydric aliphatic alcohols having 3 to 8 carbonatoms such as 1-propanol, 2-propanol, n-butan-1-ol, n-butan-2-ol,isobutan-1-ol, isobutan-2-ol, tert-butanol, pentanols and/or hexanols.The amount of blowing agent used is determined by the desired foamdensity, and the blowing agents in the reaction batch are customarilyused in amounts of approx. 0.5 to 15% by weight, based on the totalweight of the monomers used.

The precursors may further comprise customary additives. These includeantistats, antioxidants, mould release agents, lubricants, dyes, flameretardants, flow improvers, fillers, light stabilizers and organicphosphorus compounds such as phosphites or phosphonates, pigments,release agents, weathering protectants and plasticizers.

Conductive particles which prevent electrostatic charging of the foamsare a further class of preferred additives. These include metal andcarbon black particles which may also be in the form of fibres and havea size in the range from 10 nm to 10 mm, as described in EP 0 356 714A1.

Furthermore, anti-settling agents are preferred additives, since thesematerials efficiently stabilize the compositions for producingpolyacrylimide foams. These include carbon blacks, for example, KBEC-600 JD from Akzo Nobel, and Aerosils, for example, Aerosil 200 fromDegussa AG, or thickeners based on polymers, for example, high molecularweight polymethyl methacrylate.

A poly(meth)acrylimide foam according to the invention may be produced,for example, by polymerizing a mixture consisting of

-   (A) 20-60% by weight of (meth)acrylonitrile,    -   40-80% by weight of (meth)acrylic acid and    -   0-20% by weight of further vinylically unsaturated monomers, the        constituents of the components (A) adding up to 100% by weight;-   (B) 0.5-15% by weight, based on the weight of the components (A), of    a blowing agent;-   (C) 1-50% by weight, based on the weight of the components (A), of    ammonium polyphosphate and/or zinc sulphide;-   (D) 0.01-0.3% by weight, based on the weight of the components (A),    of a polymerization initiator;-   (E) 0-200% by weight, based on the weight of the components (A), of    customary additives    to give a slab and then foaming this polymer slab at temperatures of    150 to 250° C.

A further aspect of the present invention is poly(meth)acrylimidemoulding compositions having reduced flammability which compriseammonium polyphosphate and/or zinc sulphide. These thermoplasticallyprocessable moulding compositions comprise poly(meth)acrylimides havinghigh heat distortion resistance which may be obtained, for example, byreacting polymethyl methacrylate or its copolymers with primary amines.The following are representative examples of this polymer-likeimidation; U.S. Pat. No. 4,246,374, EP 216 505 A2, EP 860 821. High heatdistortion resistance can be achieved either by the use of arylamines(JP 05222119 A2) or by the use of special comonomers (EP 561 230 A2, EP577 002 A1). All of these reactions result in solid polymers which maybe foamed in a separate second step to obtain a foam using suitabletechniques known to those skilled in the art.

Poly(meth)acrylimide moulding compositions according to the inventioncomprise as essential constituent flame-retardant ammonium polyphosphateand/or zinc sulphide. Preference is given to using this constituent inthe above-detailed amounts.

Furthermore, these moulding compositions may comprise the abovementionedoptional additives. They may be provided with ammonium polyphosphateand/or zinc sulphide before, during or after the polymerization orimidation by known processes.

As previously mentioned, these moulding compositions may be foamed withthe aid of known techniques. One way of achieving this is to use theabovementioned blowing agents which, for example, may be added to themoulding compositions by compounding.

Poly(meth)acrylimide foams according to the invention may be providedwith covering layers, in order to increase, for example, the strength.Furthermore, layered materials are known which, owing solely to thechoice of the covering material, offer a certain flame retardancy. Whenthe foams according to the invention are used, the fire resistance whichis achieved by using these composite materials can be distinctlyincreased.

The covering layer used may be any known sheet-like structure which isstable under the processing parameters such as pressure and temperaturewhich are necessary for preparing the composite structure. Examplesinclude films and/or sheets which comprise polypropylene, polyester,polyether, polyamide, polyurethane, polyvinyl chloride, polymethyl(meth)-acrylate, plastics obtained by curing reactive resins, forexample epoxide resins (EP resins), methacrylate resins (MA resins),unsaturated polyester resins (UP resins), isocyanate resins andphenacrylate resins (PHA resins), bismaleimide resins and phenol resins,and/or metals, for example aluminium. Preference is further given to thecovering layer being a mat or web which comprises glass fibres, carbonfibres and/or aramid fibres, and the covering layer may also be a webwhich has a multi-layered structure.

One way of applying these fibre-containing webs to the foams is asprepregs. These are fibre mats, usually glass fibre mats or glassfilament wovens, which have been preimpregnated with curable plasticsand can be processed to give mouldings or semi-finished products by hotpressing. These include GMT and SMC.

Carbon fibre-strengthened plastics are also known which are particularlysuitable as covering layers.

The thickness of the covering layer is preferably in the range from0.1-100 mm, with preference in the range from 0.5-10 mm.

To improve the adhesion, an adhesive may also be used. However,depending on the material of the covering layer, this may not benecessary.

The poly(meth)acrylimide foams according to the invention and inparticular the layered materials comprising these foams may be used, forexample, in aircraft building and in the building of ships or railvehicles.

The foams produced in this way further pass the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853(a)(1)(i) and the toxicity requirementaccording to AITM 3.0005. In contrast to the expandable-graphite-filledsystems, a homogeneous particle distribution is possible, so that thesefoam slabs can be processed by the generally known means with regard tothe PMI foams customary on the market.

EXAMPLES Example 1

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 400 g (4.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent. (Sales: E. and P.Würtz GmbH & Co. KG, Industriegebiet, In der Weide 13+18, 55411 Bingen,Sponsheim.)

The flame retardants added to the mixture were 10,000 g (100.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. and 125 g (1.25 parts by weight) of Flameblock 10.0R (zinc sulphide)from Sachtleben. The mixture was stirred until homogeneous and thenpolymerized at 42° C. for 19.25 h in a cell formed from two glass platesof size 50×50 cm and an edge seal of thickness 1.85 cm. For completingpolymerization, the polymer was then subjected to a heating programmeranging from 40 to 115° C. for 17.25 h. The subsequent foaming waseffected at 180° C. for 2 h.

The foam obtained in this way had a density of 72 kg/m³. The heatrelease according to FAR 25.853(c) was HR=79 kWmin/m² and HRR=75 Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853(a)(1)(i) and the toxicity requirementaccording to AITM 3.0005.

Example 2

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 400 g (4.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 10,000 g (100.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. and 250 g (2.5 parts by weight) of Flameblock 10.0R (zinc sulphide)from Sachtleben. The mixture was stirred until homogeneous and thenpolymerized at 42° C. for 20 h in a cell formed from two glass plates ofsize 50×50 cm and an edge seal of thickness 1.85 cm. For completingpolymerization, the polymer was then subjected to a heating programmeranging from 40 to 115° C. for 17.25 h. The subsequent foaming waseffected at 180° C. for 2 h.

The foam obtained in this way had a density of 71 kg/m³. The heatrelease according to FAR 25.853(c) was HR=94 kWmin/m² and HRR=80 Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853(a)(1)(i) and the toxicity requirementaccording to AITM 3.0005.

Example 3

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 500 g (5.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 10,000 g (100.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. and 375 g (3.75 parts by weight) of Flameblock 10.0R (zinc sulphide)from Sachtleben. The mixture was stirred until homogeneous and thenpolymerized at 45° C. for 19.5 h in a cell formed from two glass platesof size 50×50 cm and an edge seal of thickness 1.85 cm. For completingpolymerization, the polymer was then subjected to a heating programmeranging from 40 to 115° C. for 17.25 h. The subsequent foaming waseffected at 180° C. for 2 h.

The foam obtained in this way had a density of 78 kg/m³. The heatrelease according to FAR 25.853(c) was HR=75 kWmin/m² and HRR=78 Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853(a)(1)(i) and the toxicity requirementaccording to AITM 3.0005.

Example 4

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 500 g (5.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 7500 g (75.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. and 125 g (1.25 parts by weight) of Flameblock 10.0R (zinc sulphide)from Sachtleben. The mixture was stirred until homogeneous and thenpolymerized at 46° C. for 22.5 h in a cell formed from two glass platesof size 50×50 cm and an edge seal of thickness 1.85 cm. For completingpolymerization, the polymer was then subjected to a heating programmeranging from 40 to 115° C. for 17.25 h. The subsequent foaming waseffected at 180° C. for 2 h.

The foam obtained in this way had a density of 76 kg/m³. The heatrelease according to FAR 25.853(c) was HR=108 kWmin/m² and HRR=112Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853(a)(1)(i) and the toxicity requirementaccording to AITM 3.0005.

Example 5

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 500 g (5.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 7500 g (75.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. and 375 g (3.75 part by weight) of Flameblock 10.0R (zinc sulphide)from Sachtleben. The mixture was stirred until homogeneous and thenpolymerized at 46° C. for 22.5 h in a cell formed from two glass platesof size 50×50 cm and an edge seal of thickness 1.85 cm. For completingpolymerization, the polymer was then subjected to a heating programmeranging from 40 to 115° C. for 17.25 h.

The subsequent foaming was effected at 180° C. for 2 h.

The foam obtained in this way had a density of 79 kg/m³. The heatrelease according to FAR 25.853(c) was HR=113 kWmin/m² and HRR=103Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853 (a) (1) (i) and the toxicityrequirement according to AITM 3.0005.

Example 6

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 500 g (5.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 6250 g (62.5 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. and 125 g (1.25 parts by weight) of Flameblock 10.0R (zinc sulphide)from Sachtleben. The mixture was stirred until homogeneous and thenpolymerized at 42° C. for 17.5 h in a cell formed from two glass platesof size 50×50 cm and an edge seal of thickness 1.85 cm. For completingpolymerization, the polymer was then subjected to a heating programmeranging from 40 to 115° C. for 17.25 h. The subsequent foaming waseffected at 181° C. for 2 h.

The foam obtained in this way had a density of 77 kg/m³. The heatrelease according to FAR 25.853(c) was HR=116 kWmin/m² and HRR=113Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853 (a) (1) (i) and the toxicityrequirement according to AITM 3.0005.

Example 7

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 500 g (5.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 10,000 g (100.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. The mixture was stirred until homogeneous and then polymerized at50° C. for 19.5 h in a cell formed from two glass plates of size 50×50cm and an edge seal of thickness 1.85 cm. For completing polymerization,the polymer was then subjected to a heating programme ranging from 40 to115° C. for 17.25 h. The subsequent foaming was effected at 185° C. for2 h.

The foam obtained in this way had a density of 66 kg/m³. The heatrelease according to FAR 25.853(c) was HR=84 kWmin/m² and HRR=82 Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853(a)(1)(i) and the toxicity requirementaccording to AITM 3.0005.

Example 8

1000 g (10.0 parts by weight) of isopropanol were added as a blowingagent to a mixture of 5000 g of methacrylic acid (50.0 parts by weight)and 5000 g of methacrylonitrile (50.0 parts by weight). Also added tothe mixture were 20 g (0.20 part by weight) of tert-butyl perpivalate,3.6 g (0.036 part by weight) of tert-butyl per-2-ethyl-hexanoate, 10 g(0.10 part by weight) of tert-butyl perbenzoate, 500 g (5.0 parts byweight) of Degalan BM 310 (high molecular weight polymethylmethacrylate), 0.5 g (0.005 part by weight) of benzoquinone and 32.0 g(0.32 part by weight) of PAT 1037 as release agent.

The flame retardants added to the mixture were 5000 g (50.0 parts byweight) of APP2 (ammonium polyphosphate) from Nordmann, Rassmann GmbH &Co. The mixture was stirred until homogeneous and then polymerized at45° C. for 65 h in a cell formed from two glass plates of size 50×50 cmand an edge seal of thickness 1.85 cm. For completing polymerization,the polymer was then subjected to a heating programme ranging from 40 to115° C. for 17.25 h. The subsequent foaming was effected at 196° C. for2 h.

The foam obtained in this way had a density of 69 kg/m³. The heatrelease according to FAR 25.853(c) was HR=112 kWmin/m² and HRR=112Kw/m².

The foam produced in this way also passes the smoke density testaccording to FAR 25.853(c), AITM 2.0007, the requirement of the verticalflame test according to FAR 25.853 (a) (1) (i) and the toxicityrequirement according to AITM 3.0005.

Comparative Example 1

A foam having a density of 71 kg/m³ was prepared according to DE 33 46060 using 10 parts by weight of DMMP as flame retardant.

For this example, a mixture of equal molar parts of 5620 g (56.2 partsby weight) of methacrylic acid and 4380 g (43.8 parts by weight) ofmethacrylonitrile had added to it 140 g (1.4 parts by weight) offormamide and 135 g (1.35 parts by weight) of water as blowing agents.Also added to the mixture were 10.0 g (0.100 part by weight) oftert-butyl perbenzoate, 4.0 g (0.0400 part by weight) of tert-butylperpivalate, 3.0 g (0.0300 part by weight) of tert-butylper-2-ethylhexanoate and 10.0 g (0.1000 part by weight) of cumylperneodecanoate as initiators. Furthermore, 1000 g (10.00 parts byweight) of dimethyl methanephosphonate (DMMP) were added to the mixtureas flame retardant. Finally, the mixture contained 20 g (0.20 part byweight) of release agent (MoldWiz) and 70 g (0.70 part by weight) ofZnO.

This mixture was polymerized at 40° C. for 92 h in a cell formed fromtwo glass plates of size 50×50 cm and an edge seal of thickness 2.2 cm.For completing polymerization, the polymer was then subjected to aheating programme ranging from 40 to 115° C. for 17.25 h. The subsequentfoaming was effected at 215° C. for 2 h.

The resulting foam had a density of 71 kg/m³.

The heat release according to FAR 25.853(c) was HR=211 kWmin/m² andHRR=243 Kw/m². Also, the foam prepared in this way fails the smokedensity test according to FAR 25.853(c), AITM 2.0007 and also therequirement of the vertical flame test according to FAR 25.853(a)(1)(i).

Comparative Example 2

For this example, a mixture of 5700 g (57.0 parts by weight) ofmethacrylic acid and 4300 g (43.0 parts by weight) of methacrylonitrilehad added to it 140 g (1.4 parts by weight) of formamide and 135 g (1.35parts by weight) of water as blowing agents. Also added to the mixturewere 10.0 g (0.100 part by weight) of tert-butyl perbenzoate, 4.0 g(0.040 part by weight) of tert-butyl perpivalate, 3.0 g (0.030 part byweight) of tert-butyl per-2-ethylhexanoate and 10 g (0.100 part byweight) of cumyl perneodecanoate as initiators. Furthermore, 1000 g(10.00 parts by weight) of dimethyl methanephosphonate (DMMP) were addedto the mixture as flame retardant. Finally, the mixture contained 15 g(0.15 part by weight) of release agent (PAT 1037) and 70 g (0.70 part byweight) of ZnO.

This mixture was polymerized at 40° C. for 92 h in a cell formed fromtwo glass plates of size 50×50 cm and an edge seal of thickness 2.2 cm.For completing polymerization, the polymer was then subjected to aheating programme ranging from 40 to 115° C. for 17.25 h. The subsequentfoaming was effected at 220° C. for 2 h. The resulting foam had adensity of 51 kg/m³.

The heat release according to FAR 25.853(c) was HR=118 kWmin/m² andHRR=177 Kw/m². Also, the foam prepared in this way fails the smokedensity test according to FAR 25.853(c), AITM 2.0007 and also therequirement of the vertical flame test according to FAR 25.853(a)(1)(i).

Comparative Example 3

The procedure was substantially that of comparative example 1, exceptthat the foaming was effected at 210° C. and the density of theresulting foam was as a result 110 kg/m³.

The heat release according to FAR 25.853(c) was HR=267 kWmin/m² andHRR=277 Kw/m². The foam prepared in this way also fails the smokedensity test according to FAR 25.853(c), AITM 2.0007.

1-30. (canceled)
 31. A composition for producing poly(meth)acrylimidefoams having reduced flammability, comprising polymerizable mixtures of(meth)acrylic acid and (meth)acrylonitrile, a blowing agent, acrosslinker, at least one polymerization initiator, and ammoniumpolyphosphate.
 32. The composition according to claim 31, wherein theammonium polyphosphate is present in an amount from 1 to 300% by weight,based on the weight of the monomers.
 33. The composition according toclaim 31, wherein the ammonium polyphosphate is present in an amountfrom 5 to 200% by weight, based on the weight of the monomers.
 34. Thecomposition according to claim 31, wherein the ammonium polyphosphate ispresent in an amount from 25 to 150% by weight, based on the weight ofthe monomers.
 35. A composition for producing poly(meth)acrylimide foamsand moulding compositions having reduced flammability, comprising zincsulphide.
 36. The composition according to claim 35, wherein the zincsulphide is present in an amount from 0.1 to 20% by weight, based on theweight of the monomers.
 37. The composition according to claim 35,wherein the zinc sulphide is present in an amount from 0.5 to 10% byweight, based on the weight of the monomers.
 38. The compositionaccording to claim 35, wherein the zinc sulphide is present in an amountfrom 1 to 5% by weight, based on the weight of the monomers.
 39. Acomposition for producing poly(meth)acrylimide foams and mouldingcompositions having reduced flammability, comprising zinc sulphide andammonium polyphosphate.
 40. The composition according to claim 39,wherein the zinc sulphide is present in an amount from 0.1 to 20% byweight, based on the weight of the monomers, and the ammoniumpolyphosphate is present in an amount from 1 to 300% by weight, based onthe weight of the monomers.
 41. The composition according to claim 39,wherein the zinc sulphide is present in an amount from 0.5 to 10% byweight, based on the weight of the monomers, and ammonium polyphosphateis present in an amount from 5 to 200% by weight, based on the weight ofthe monomers.
 42. The composition according to claim 39, wherein thezinc sulphide is present in an amount from 1 to 5% by weight, based onthe weight of the monomers, and the ammonium polyphosphate is present inan amount from 25 to 150% by weight, based on the weight of themonomers.
 43. The composition according to claim 31, further comprisingone or more flame retardants.
 44. The composition according to claim 43,wherein the one or more flame retardants are one or more phosphoruscompounds.
 45. The composition according to claim 44, wherein the one ormore phosphorus compounds are selected from phosphines, phosphineoxides, phosphonium compounds, phosphonates, phosphites, phosphates, ormixtures thereof.
 46. The composition according to claim 31, furthercomprising dimethyl methanephosphonate.
 47. The composition according toclaim 31, further comprising resorcinol bisdiphenylphosphate.
 48. Thecomposition according to one claim 31, further comprising ananti-settling agent.
 49. The composition according to claim 48, whereinthe anti-settling agent is a high molecular weight polymethylmethacrylate.
 50. The composition according to claim 48, wherein theanti-settling agent is an Aerosil.
 51. The composition according toclaim 48, wherein the anti-settling agent is carbon black.
 52. Thecomposition according to claim 31, wherein the blowing agent is selectedfrom an aliphatic alcohol having 3 to 8 carbon atoms, urea, monomethyl-or N,N′-dimethylurea, or formamide.
 53. A moulding prepared from thecomposition according to claim
 35. 54. A poly(meth)acrylimide foamobtained from polymerizing and foaming the composition according toclaim
 31. 55. A poly(meth)acrylimide foam obtained by foaming thecomposition according to claim
 35. 56. A layered material comprising alayer of a poly(meth)acrylimide foam according to claim
 54. 57. Anautomobile comprising the poly(meth)acrylimide foam according to claim54.
 58. A rail vehicle comprising the poly(meth)acrylimide foamaccording to claim
 54. 59. A watercraft comprising thepoly(meth)acrylimide foam according to claim
 54. 60. An aircraftcomprising the poly(meth)acrylimide foam according to clam 54.